There are piezoelectric elements having a configuration in which a piezoelectric layer made of a piezoelectric material having an electromechanical conversion function, for example, a crystallized piezoelectric material is placed between two electrodes. Such piezoelectric elements are mounted on liquid ejecting heads as, for example, a flexure-mode actuator device. As a representative example of the liquid ejecting head, for example, there are ink jet recording heads in which a vibrating plate configures a part of a pressure generation chamber communicating with a nozzle opening which discharges ink droplets, and this vibrating plate is deformed by a piezoelectric element to pressurize an ink in the pressure generation chamber to thus discharge ink droplets from the nozzle opening.
As a piezoelectric material used in such piezoelectric elements, for example, lead-based piezoelectric ceramics represented by lead zirconate titanate (PZT) are usually used (for example, see JP-A-2001-223404). However, the development of a piezoelectric material containing no lead, that is, a lead-free piezoelectric material advances from the viewpoint of environmental problems. Examples of the lead-free piezoelectric material include barium titanate (BaTiO3) having a perovskite structure represented by ABO3 and bismuth ferrate (BiFeO3) (for example, see JPA-2009-252789).
However, in the case of the lead-free piezoelectric material, the leak current is large and the displacement amount is insufficient as compared to lead zirconate titanate (PZT). Accordingly, for example, ink jet recording heads have a problem in that large liquid droplets are not easily discharged. In order to improve leakage characteristics and displacement characteristics of such a lead-free piezoelectric material, a technology of substituting a part of an element occupying the A-site of the perovskite structure and an element occupying the B-site with an element having different ion valency and a different ionic radius is proposed (for example, see JP-A-2010-214841 and JP-A-2011-035385).
However, in order to obtain leakage characteristics and displacement characteristics comparable to a lead (Pb)-based piezoelectric material, it is necessary to further examine and optimize the selection of a substitution site or a substitution element in the perovskite structure, a substitution amount and the like. Such a problem is not limited to piezoelectric elements which are mounted on ink jet recording heads, but exists also in other liquid ejecting heads which discharges liquid droplets other than an ink, liquid ejecting apparatuses, and piezoelectric elements which are mounted on sensors.
An object of the invention is to provide a piezoelectric element, a liquid ejecting head, a liquid ejecting apparatus, an actuator, a sensor, and a piezoelectric material in which the leak current can be reduced and the displacement amount can be improved in view of the circumstances.